In arctic and antarctic regions, sewage disposal is a considerable problem. In general, it is not possible to pipe sewage from houses and other buildings to a central treatment plant due to the fact that the sewage would freeze in the pipes. Furthermore, in areas where the permafrost extends to a significant depth, it is not feasible to lay sewage pipes. Indeed, even where sewage pipes could be laid to a sufficient depth to avoid freezing of the sewage, in general, it is not practicable to provide a central sewage treatment plant, due to the fact that the liquid contents of the treatment plant would freeze. Various attempts have been made to overcome these problems without success. Typically, sewage tanks are provided in houses or buildings, or indeed, below the foundations of such buildings. Sewage is subsequently pumped from these tanks. However, a major problem with such tanks is that the sewage contents of the tanks freeze. This, in general, causes rupturing of the tank, which leaves the tank unusable.
There is therefore a need for a sewage tank which overcomes these problems.